The response of the immunological apparatus to antigenic challenge is characterized by the synthesis of both specific antibody and non-specific immunoglobulin. The current proposal is designed to obtain additional information at the cellular level concerning the non-specific aspects of the response. Experiments will first be run to determine the range of stimuli which can elicit the non-specific response. These will be followed by studies employing various ablative and reconstructive procedures as well as transfers of lymphoid cells to identify the cell types involved in the response and define their roles. In addition the relationship of non-specific and specific immunoglobulin synthesis will be determined through studies involving tolerance, ontogeny, and immunosuppression. The possible antibody nature of the non-specifically stimulated immunoglobulin will be studied.